1. Field
This patent specification relates to a method and a device for cleaning a charging brush which charges a surface of a photoconductive element to be used in an electrophotographic process of an image forming apparatus, such as a copying machine, a facsimile, and a printer, etc., and more particularly to a method and a device that can effectively clean a charging brush at a reduced cost.
2. Discussion
A roll-shaped brush structure, having a large number of elastic, electrically conductive threads at its outer periphery to charge a surface of a photoconductive element used in an electrophotographic printing process, is commonly known. The charging brush contacts the surface of the photoconductive element and applies a high voltage to the surface thereof so as to cause corona discharge, thereby electrostatically charging the surface of the photoconductive element.
The useful life of the charging brush ends when it becomes unable to cause effective corona discharge due to fouling, such as toner or an additive to toner adhered to the conductive threads of the brush. As described in Japanese Patent Laid-Open Publications Nos. 6-289755 and 7-89627, it may be comparatively easy to remove fouling from a charging roller that does not have a brush structure, by washing the charging roller. However, it is difficult to recycle a charging brush which is at the end of its useful life.
The reason why it is difficult to recycle a charging brush which is at the end of its life due to the above-described fouling by material adhering to conductive threads of the brush, is believed to be as follows.
It is believed that the fouling material needs to be removed before a used charging brush could be reused. A charging brush is generally constructed of a pile fabric of conductive threads, which is secured to a metal sheet or is wound around a shaft in a shape of a roller. An attempt can be made to remove fouling adhered to a charging brush by using an air blow or by scraping off with a scraper. However, when the fouling is removed by the above-mentioned methods, it is likely that at least some of the conductive threads will come out as well, thereby causing abnormal discharge or cutting off an exposure optical path in an electrophotographic printing process. When the fouling is swept by the scraper, tips of the conductive threads might be scraped which may damage the conductive threads and cause abnormal discharge. In addition, because the conductive thread is deformed due to an excessive force exerted thereon, an outside shape or dimensions set for the charging brush may not be maintained.
Various proposals have been made to address the above-mentioned problems. When a recycling process to reuse a charging brush is performed, it is important that costs involved are kept to a minimum by decreasing the work needed for the process. It is believed that costs cannot be satisfactory decreased with the known prior art technology in which a specific jig is used or the amount of work is not sufficiently decreased.
A method for reducing total costs involved in recycling work has been proposed. According to this method, a current leak caused when a photoconductive drum is damaged is checked at the time when a changing brush is cleaned. Specifically, a current leak check is carried out by running a current. When a photoconductive element is damaged such that a portion of a photoconductive layer thereof has come off and the ground (GND) layer is exposed, an excessive current is fed to an exposed portion of a ground (GND) layer from a charging brush. At least a portion of the charging brush can burn or otherwise be damaged due to the passage of the excessive current, and thereby the charging brush may become unsuitable for further use. Also, the photoconductive element may become unsuitable for further use because burnt out conductive threads may stick at the place where the portion of the ground (GND) layer of the photoconductive element is exposed.
As described above, the prior proposal may lead to making unusable both the photoconductive element and the charging brush by performing a cleaning of the charging brush and a current leak check of the photoconductive element at the same time.
An object of the disclosure herein is to overcome the above-mentioned and other problems.
The system and method disclosed herein advantageously provide a novel charging brush cleaning device wherein a charging brush used in an electrophotographic printing process can be cleaned effectively by reducing the total costs involved without decreasing the performance of the charging brush.
According to preferred embodiments, fouling adhered to a charging brush is removed by vibrations caused in a portion of the charging brush by an alternating electric field applied thereto.